The invention relates to a method for providing an environmental map for a vehicle, to a corresponding device and to a corresponding computer program.
Motor vehicles have at their disposal a range of driver assistance systems which warn the driver about collisions and, if appropriate, attempt to avoid collisions by means of interventions. In order to make these functions available, knowledge of the environment of the vehicle is decisive for such driver assistance systems. In order to represent the environment for driver assistance systems it has already been proposed to examine subsections of the environment by use of sensors and to detect their occupancy or non occupancy, if appropriate with the specification of a probability of occupancy. The representation of the environment is then implemented by what is referred to as an environmental map (sometimes also referred to as a grid) that comprises cells which are each in turn assigned to the subsections. The information on the occupancy of the respective subsection is then assigned to the corresponding cell. The occupancy information which is assigned to a cell is typically acquired by a sensor system, for example an ultrasonic sensor or a radar system.
The environmental map which is acquired in this way with occupancy information can serve as a basis for highly automated driving.
The environmental map and the cells thereof with assigned occupancy probabilities are stored in the vehicle and, if appropriate, also in a central server after transmission.
DE 10 2006 061 390 A1 discloses an environment detection system in which a selection unit determines a selected spatial area of the environment about which information is preferably required. A control unit is able to actuate a sensor system in such a way that information about the selected spatial area is acquired. In this system, occupancy information is determined only for selected areas of an invariable environmental map.
DE 10 2011 113 016 A1 discloses a method for representing the surroundings of a vehicle in which surroundings data is acquired and stored in a hierarchical data structure. The detail level of areas of the data structure is determined as a function of properties of the objects identified there. The section of the environment of the vehicle which is represented by the data structure remains the same here, more details on areas of the environment in which objects have been identified are merely made available.
A disadvantage of the existing methods and systems for environmental maps is that they have to generate and process large quantities of data in real time despite the only limited computational and storage capacities in vehicles.
The object on which the invention is based is to provide a method with which environmental maps for vehicles can be generated and updated more efficiently in terms of computing and storage.
This and other objects are achieved by embodiments of the invention disclosed herein.
In one aspect, a method provides an environmental map for a vehicle, wherein the environmental map represents a section of the environment and comprises cells which are each assigned to a subsection of the section of the environment of the vehicle. Each cell is assigned occupancy information which is based on the probability of the presence of an object or of part of an object in the subsection assigned to the respective cell. The vehicle includes a group of at least two driver assistance systems which are each configured to assume an active state and an inactive state and which, in the active state, require occupancy information about sections of the environment of the vehicle which each at least do not overlap completely. The method determines the driver assistance system or systems which is/are in the active state; determines the section of the environment which the environmental map is intended to represent, on the basis of the section or sections about which the driver assistance system or systems requires/require occupancy information in the active state. The section of the environment which the environmental map is intended to represent comprises the section or sections about which the driver assistance system or systems requires/require occupancy information in the active state.
The method permits the environmental map to be configured in accordance with requirements. Only the areas of the environment about which information is actually required are represented by cells of the environmental map. The section of the environment which is represented by the environmental map is therefore not limited to permanently predefined geometric shapes. In the prior art these would typically be rectangular shapes. Instead, the section can assume any desired geometric shape. This has the advantage that sections of the environment which would not be considered by driver assistance systems also do not take up any capacities in the storage and processing of the environmental map. The capacities which become free in this way can be used to represent more precisely the sections of the environment about which occupancy information is actually required; for example by finer resolution (that is to say smaller subsections) and/or more informative but more computationally intensive signal processing. The existing storage and computing capacities are therefore used more efficiently.
The environmental map which is produced can be referred to as a “grid carpet”. The sections about which the respective driver assistance systems require occupancy information (sometimes also referred to as partial grids) can have different and situationally variable edge lengths here as well as different and situationally variable sizes and shapes of the subsections (square, rectangular, logarithmic), and also different and situationally variable dimensions (1D, 2D, 2.5D, 3D). The cell size can increase exponentially within a section as the distance from the vehicle increases, with the result that in the immediate vicinity of the vehicle there is a higher cell density than at a large distance from the vehicle.
The sections about which the respective driver assistance systems require occupancy information can lie in a situationally planar fashion on the ground or be “upright” in space or curved.
The method can also comprise the following act of making available a storage structure for receiving occupancy information for the specific environmental map. The occupancy information can be stored in a data structure which is adapted to the environmental map. For example, information on the geometry of the environmental map can be stored in a first storage area. This information is, in particular, the description of the outer contour and, if appropriate, a generic mathematical or other general description of the situation and shape of the subsections to which the cells are assigned. The cells themselves can be created and identified in a second storage area, in particular with consecutive numbering. The cells can be in the form of entries in a database or storage structure. The entire database or storage structure can then represent the environmental map. For areas of the environment which do not lie in the represented section, no cells and therefore no storage space are provided. The method can also comprise the act of detecting occupancy information for subsections of the environment using sensors; storing the occupancy information in the storage structure which is made available.
In one further development, for each section about which a driver assistance system requires occupancy information in the active state, the subsections which lie in the respective section are also predefined. The method then also comprises the act of determining the subsections of the environment which the environmental map is intended to represent; and in areas in which sections about which driver assistance systems in the active state require occupancy information overlap, selecting those predefined subsections which are smallest in size (that is to say have the smallest surface content or the smallest circumference). In areas in which there is no overlap, subsections are typically selected which lie in these areas or are closest to them.
It will frequently be the case that driver assistance systems require different spatial resolutions of the occupancy information and therefore predefine the subsections for the section of the environment about which they require occupancy information. The predefinition of the subsections can be done by defining the geometric shape and position of the individual subsections or by use of a generic mathematical formula or mathematical description. Overlaps can occur during the determination of the section of the environment which the environmental map is intended to represent and which typically comprises at least the sections about which the active driver assistance systems require occupancy information. In other words, the sections of the environment about which the active driver assistance systems require occupancy information typically overlap. In these areas, the subsections which provide finer resolution, that is to say the smaller size for the subsections, are then selected. In this way, the most stringent requirement of the assistance systems of the resolution is taken into account.
Furthermore, in the case of overlaps of sections it may be the case that edges of sections or subsections of one assistance system do not coincide with the edges of sections or subsections of another assistance system. In this case there may be provision to maintain the residual subsections which are produced in the case of one section in order to maintain the regularity of the section which is covered and is to be continued (that is to say the section with the greater size of the subsections). Alternatively, the sections about which the driver assistance systems require occupancy information in the active state can also be defined in such a way that the boundaries of sections with relatively small subsections coincide with the edges of subsections of sections with relatively large subsections.
In one development, the determination of the occupancy information which is assigned to a cell of the environmental map is based on measurements of a first sensor and on measurements of a second sensor. The information which is received from two different sensors, typically from two different sensor systems, is therefore combined in an occupancy information item. For example a camera, an ultrasonic sensor, a radar system, a lidar system, an infrared sensor or similar sensors can be used as first or second sensors for the environment.
In another development, the method also comprises the act of receiving the direction of movement of the vehicle; wherein the determination of the section of the environment which the environmental map is intended to represent is additionally dependent on the received direction of movement of the vehicle. Driver assistance systems can be configured for various directions of movement of the vehicle, for example for forward travel and for reverse travel. Therefore, such a driver assistance system generally requires occupancy information of sections of the environment in front of the vehicle and sections of the environment behind the vehicle. However, the driver assistance system does not require the occupancy information for forward travel at the same time as the occupancy information for reverse travel. Sections of the environment which are required only for a specific direction of movement of the vehicle, for example for reverse travel, may not be included in the environmental map in the case of forward travel of the vehicle. The environmental map which is produced in this way then does not represent the sections of the environment which are not required for the direction of movement at that time.
In a refinement, the method comprises, in particular, the determination of the geometric shape of each subsection, in particular as a function of the received direction of movement. The adaptation of the environmental map can therefore also take place in such a way that the subsections of the environment are adapted to the direction of the movement. All the subsections of the prior art typically always have the same geometric shape, for example each subsection is square or rectangular. In the method according to the invention, it is possible to provide instead that subsections for one direction of movement are given one geometric shape and for another direction of movement are given a different geometric shape. In the case of forward travel, it is therefore possible, for example, for the environment to be divided into elongate rectangles as subsections, while in the case of reverse travel the environment is divided into squares. An application for this would be, for example, in the case of parking, in which relatively fine division of the environment in the reverse direction is particularly helpful, since the driver's view in the reverse direction is frequently more restricted than in the forward direction.
In one development, the method also comprises the act of receiving the steering angle of wheels of the vehicle; wherein the determination of the section of the environment which the environmental map is intended to represent is additionally dependent on the received steering angle of the vehicle. Such a procedure is appropriate, in particular, when a driver assistance system requires, for example, occupancy information for the section of the future travel profile. Instead of selecting the represented section of the environment in such a way that all the possible corners are covered by the environmental map, depending on the steering angle (and therefore cornering) only that section of the environment is represented which is travelled through in the case of the steering angle at that time, if appropriate somewhat widened for unpredictable deviations during the cornering. The section of the environment can be, for example, a rectangle which is bent in accordance with the steering angle. In this way, the represented section of the environment is reduced in size to the area which is actually relevant for driver assistance systems. The computing resources and storage capacity which are present in the vehicle can be used more efficiently. In one development, the method can also comprise the act of determining the geometric shape of each subsection, in particular as a function of the received steering angle. For example, the subsections can be curved rectangles in accordance with the future travel path in the case of the steering angle at that time and can adopt the geometric shape of the represented section in a reduced form. In this way, a simplified assignment of cells of the environmental map to the subsections is made possible.
In another development, the method also comprises the act of detecting objects in the environment of the vehicle; wherein the determination of the section of the environment which the environmental map is intended to represent is additionally dependent on the detected objects in the environment of the vehicle. In this way it is made possible for the represented section of the environment to be enlarged where objects are located. If, for example, part of an object is detected by the represented section and, for example, the object is detected as another road user, or this is suspected, the represented section of the environment can be expanded, with the result that this road user is located completely in the represented section of the environment. This permits the assistance systems which are concerned with other road users to better track and analyze the road users which are otherwise not completely represented. This concept can also be transferred to the geometric shape of each subsection.
The method then also comprises the act of determining the geometric shape of each subsection, in particular as a function of detected objects in the environment of the vehicle. For example, the subsections can be selected to be smaller in the section of the environment in which an object has been detected, in order to permit the classification or tracking of the object more precisely. This permits the use of computing capacities and storage capacities where driver assistance systems profit particularly therefrom.
In another development, the environmental map comprises at least two planes, wherein each plane represents a section of the environment and comprises cells which each represent a subsection of the respective section of the environment of the vehicle, wherein each cell is assigned occupancy information which is based on the probability of the presence of an object or of part of an object in the subsection which is assigned to the respective cell. The method also comprises the act of determining the occupancy information for each cell, in particular wherein the occupancy information for cells of a plane is based on measurements of one by at least two (different) sensor systems. This makes it possible for a section of the environment to be represented repeatedly, for example twice, in each case in a plane. This can serve to separate occupancy information from sensors. For example, the occupancy information from ultrasonic sensors can be assigned to cells of a first plane, and occupancy information relating to the same section of the environment from camera sensors can be assigned to a second plane. Furthermore, the occupancy information of groups of sensors can be assigned to planes. The cells of a specific plane can therefore be allocated the combination of occupancy information items from at least two sensors. Furthermore, this permits occupancy information of the same sensor to be assigned in cells of different planes. The occupancy information can therefore be used repeatedly. The combination and selection of occupancy information of various sensors for one plane can therefore fulfill the requirements which a driver assistance system makes of the environmental map.
In this respect it is possible to provide that, in the method, occupancy information from a first group of sensors whose generation takes approximately the same first time period is to be assigned to the cells of a first plane. Occupancy information from a second group of sensors whose generation takes, in turn, a second time period is assigned to the cells of a second plane. In this way, given limited computational capacities and storage capacities it is possible to make gradations with respect to the real time provision of occupancy information from various sensors. Data from those sensors which require a relatively long processing time is not made available as frequently as the data of those sensors which require a relatively short processing time.
In another aspect, a device includes electronic processing unit and at least one interface with a sensor system, wherein the device is configured to carry out one of the methods described above. The electronic processing unit can be a computer, a microcontroller, dedicated circuits or the like. The electronic processing unit can be configured in terms of programming technology to execute one of the illustrated methods.
In another aspect, a computer program is configured to cause, when it is executed, a computer to execute one of the presented methods. For this purpose, the computer program can include machine readable instructions.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.
Identical reference symbols relate to corresponding elements in all the figures.